1. The sales decay for a product is given by S = 50,000e-0.6x, where S is the monthly sales (in dollars) and x is the number of months that have passed since the end of an advertising campaign. What will sales be 6 months after the end of the campaign?
2. If $1000 is invested at 12%, compounded monthly, the future value S at any time t (in years) is given by
S = 1000(1.01)12t
How long will it take for the amount to double?
3. With data from the International Data Base of the U.S. Bureau of the Census, the accompanying figure shows a scatter plot of actual or projected world population (in billions) in 5-year increments from 1950 to 2050 (x = 0 in 1945). Which of the following functions would be the best model: exponential growth, exponential decay, logarithmic, or logistic? Explain.

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